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Casting ingots


#1

I’ve finally gotten to the point where I’m casting ingots, but I’ve
got a question or two about the ingot itself. When I pull it out of
the mold, I quench it, pickle it file the flash off and scratchbrush
it. When I’m through I still have numerous small pits in the ingot
and flow marks. Is this normal? And if not normal, what could I be
doing wrong? Thanks for all the help to date.

Richard, in chilly Michigan, enjoying the cold.


#2

Hi Richard Do you use an open horizontal ingot mold or a vertical
adjustable one. The technique is a little different. If you use the
open horizontal one, you can put a wall made from a copper plate to
stop the flow of molten metal to make a thick ingot. Put oil then
wipe it with a cloth and try to not heat to much the mold. If there
is flow marks you should heat more your metal or pour it faster in
the mold. The secret in pouring ingots is to optain the good
temperature and to pour the metal in one regular and continious
move. For all kind of ingot molds I never heat it, just warm it by
placing the mold close by the crucible when heating. Put a little oil
(kind of sewing machine one). Use a reducing flame with a clean
crucible put a pinch of borax during the melting. 22 years of
training students tell me these simple rules. Hope this helps


#3

Hi Richard and All, I have been following the posts on ingots with
interest wondering where to respond. Even if you do all your work
from milled sheet and wire stock, your metal always starts from a
casting…the Ingot! All the rules of casting apply to the ingot. If
you look at an ingot mold made for pouring a blank to roll into sheet
you will see a “funnel” portion at the top of the mold. The kind of
ingot mold I have can be flipped over to pour blanks for rolling wire
and they also have the same “funnel”. This tapered area at the top is
helpful for improving your aim but it is really there to provide a
button or reservoir of molten metal while the ingot is cooling and
shrinking. By using 8th grade geometry and your specific gravity
tables you can calculate how much you need to fill the ingot and the
button area. After the pour has cooled, cut off the button and mill
the rest. If you don’t want the entire depth of the ingot you can
place a spacer at the bottom made from steel. A little might leak by
but you can easily file it off and be on your way. The flow marks and
pits can be caused by a number of things. First, the ingot mold must
be hot enough to allow the pour without forming the cooling wrinkles
you mentioned. Also you might have too much soot or mold release on
the walls of the ingot mold. Slight impurities can and do react with
the molten metal and cause gas pockets and give you small dimples and
can even force their way into the metal while it is still molten, not
to be discovered until you are polishing your final piece! I have had
that unfortunate learning experience. Happy pouring and
rolling…John, J.A.Henkel Co., Inc. Moldmaking Casting Finishing,
Producing Solutions for Jewelry Artists